More info on my Fisher 400, and some questions

My original plan was to sell most of my Fisher stash and just keep the two integrateds that had been maintained over the years. The 400 has always been a lovely piece but given it is unrestored and all I read about time bomb rectifiers, I did not feel at ease using it without putting a lot of money into it.

Yesterday I ran across some info about there being at least three variants of 400, with units having a S/N over 48,000 having more dependable rectifiers and a better tuner section. Is this true?

If it is, I might be in luck. Mine has S/N 60966. Sounds like a fairly late unit. Can anyone tell me any details about such a unit?

Last night as I ran it I kept checking the transformers. All three were stone cold. Plenty of heat off the 7868 outputs but nothing that seemed abnormal there. I am planning to keep whatever tube unit I have in rotation one the variac at 110v. Would it be safe to run my late production, unrestored 400 under these conditions?

Posts stating "absolutely not, it is ticking time bomb, send it to me for safe disposal" will be cheerfully ignored....

Count the number of 6AU6s. Later ones have an additional tube. If it has three across the middle, it's a later one.

They are great units and, hey, they have tuners.

Here is pix of late model

See attached.

Late unit for sure.

So assuming this has the silicon rectifiers, if the transformers stay cool, the outputs look good is it fairly safe to run at 110v or might there be other nasty things happening that I would not be aware of just by listening?

Honestly the rectifiers aren't that big of a problem. It costs less than a buck in parts to replace them. Its the filter capacitors that are a bigger concern. If they fail, it can short things out and do some damage. I'd also not neccesarily trust original coupling capacitors without at least testing them. If they get leaky, the bias on the tubes will go way off and the tubes can overload in a bad way. If its bad, you will hear it but it can be slightly off, enough to damage the tube long term, but not enough to notice immediately. Honestly, 50 year old equipment around here gets a refurb if I want to use it. I just do not trust those old parts to not go bang and cost me a lot of money long term. A rebuild is generally cheaper than trying to replace transformers and things if stuff doesn't fail in a graceful manner.

gadget73 said:

Honestly the rectifiers aren't that big of a problem. It costs less than a buck in parts to replace them. Its the filter capacitors that are a bigger concern. If they fail, it can short things out and do some damage. I'd also not neccesarily trust original coupling capacitors without at least testing them. If they get leaky, the bias on the tubes will go way off and the tubes can overload in a bad way. If its bad, you will hear it but it can be slightly off, enough to damage the tube long term, but not enough to notice immediately. Honestly, 50 year old equipment around here gets a refurb if I want to use it. I just do not trust those old parts to not go bang and cost me a lot of money long term. A rebuild is generally cheaper than trying to replace transformers and things if stuff doesn't fail in a graceful manner.

Click to expand...

I'm with above. I rebuild the PS and check coupling caps.

OK, exactly the type of advice I was looking for. I will stick with my X202B for further tube listening. It has had work done on it a few times over the years, some bad or dodgy caps swapped out, etc. The guys who worked on it knew their stuff. On page two of this thread there is a shot of the parts that have been changed

http://www.audiokarma.org/forums/showthread.php?t=416351

+3 on the coupling caps and PS rebuild. About $30 in parts (not including can caps) and you are set. About 2 hours bench time to change the stuff out. The 400 is one of the easier FISHER's to rebuild. Do it in stages and you can notice the incremental changes.

There were 2 MAJOR Variations of the 400. <48000 and >48001. Like noted above the higher numbered version has an additional IF stage with a 3rd 6au6. No real difference otherwise.

Larry

Is it worth getting the Metalbone kit? I would have a competent tech do the work.

If the 400 is easy and cheap to restore I will probably hang onto it. It is probably safe to say I will never come across a nicer one again, and having a functioning tube tuner section is a big bonus. I originally thought it was a lesser pice but just like my X101C I now see it has quite a following. I guess there is a case to be made for having a 400, X101C and X202B!

Raynald said:

Is it worth getting the Metalbone kit? I would have a competent tech do the work.

If the 400 is easy and cheap to restore I will probably hang onto it. It is probably safe to say I will never come across a nicer one again, and having a functioning tube tuner section is a big bonus. I originally thought it was a lesser pice but just like my X101C I now see it has quite a following. I guess there is a case to be made for having a 400, X101C and X202B!

Click to expand...

You can never have too many Fisher pieces.

Right now I have two 400 receivers, two X202B amps and one 500B receiver in need of a faceplate. I love them all.

One 400 has been updated and has a mint wooden case, the other works but needs an update. One X202B has been worked on and the other needs an overhaul, having a burned smell from under the chassis. The 500B was gotten today and needs an overhaul, as the selenium rectifier is still in use.

I'm constantly on the look for Scott and Fisher pieces . . .

Cheers

Yes on the metalbone kit, if your an occasional tinkerer that isn't comfortable looking up parts. It won't come with the filter caps tho. But you can replace them with individual caps underneath or go with new custom can from Hayseed Hamfest. 3rd option would be to restuff the cans with individual caps. the metalbone kit has instructions so you can do it yourself. Good learning tool.